TopBand: 160/80 shunt fed tower?

[Jon Zaimes AA1K]

Hi Jim...My first shunt-fed tower was similar to yours (in Connecticut,
1978). It was 70 feet of Rohn 25 with a 204BA on top and a 4-el 15m Wilson
yagi a few feet above that. As I recall the 160m shunt was up about 40 feet,
out about 16-18 inches, maybe more. 

I know the 80m shunt was a lot shorter; only about 15 or 20 feet up perhaps,
and out maybe 12 or 18 inches.

Had about sixty 1/4 wave (for 160m) radials (copper-clad steel electric
fence wire, laid on the ground in woods). With the top loading, it probably
was close to being an electrical 1/4 wave on 160. It was a fine radiator.
Brought my country total up to about 83 on Top, back when that was a big
number, before moving to Delaware in '81.

On 80m, this tower works out to be about 1/2 wave electrical length. So it
must have had great low-angle radiation. It was a super antenna for working
the long haul -- VK, ZL, and JA.  But for working Europe, it was terrible.
I'd call and call and call -- and they just couldn't hear me. Finally went
back to using a dipole at 50 feet in the trees to finish up 80m DXCC.

73/Jon AA1K

At 09:03 AM 11/26/96 +0000, you wrote:
>Hello Topbanders,
>
>I have a 65 ft tower with a TH7 and 40-2CD on top and 16 radials from 
>1/8 to 1/4 wavelength long.  I have shunt fed it for 160m with a 
>jumper across the 18 inch spaced shunt at abt 50 ft.  It seems to
> work pretty good.  The SWR is almost flat across the entire 160m band.
>  Is that typical?
>
>I also tried to add an 80 meter shunt on the opposite side of the 
>tower.  I havn't been able to find an optimum jumper point on the 
>shunt.  The lowest SWR has been 2:1 and the bandwith is quite narrow 
>(which is OK).  The performance has been poor.  I probably just need
> more time to refine it.  My question regards interaction between the 
>two shunts.  It appears that the 160m performance has decreased since
> I added the 80 m shunt.  Could this be true or is it just my biased
> judgement or band conditions?
>
>Have any of you had success with a combo 160/80 m shunt fed tower?  
>Any guess where the 80 m jumper would be with 18 inch spacing?
>
>Thanks for reading my questions and for your response if you can 
>help.
>
>73,
>
>Jim Hood, K5TT
>President, Oklahoma DX Association
>wv5s@icon.net
>Past operations: KC6SS, V63SH, /XE, /WH6, /NH7, /KP2
>Previous calls: WV5S, W0PUD, W7KDH, K5TWD
>USA-CA # 432
>
>--
>FAQ on WWW:               http://www.contesting.com/topband.html
>Submissions:              topband@contesting.com
>Administrative requests:  topband-REQUEST@contesting.com
>Sponsored by Akorn Access, Inc & KM9P
>



--
FAQ on WWW:               http://www.contesting.com/topband.html
Submissions:              topband@contesting.com
Administrative requests:  topband-REQUEST@contesting.com
Sponsored by Akorn Access, Inc & KM9P